How do you contract out PCB assembly?

[LoveLaika]

Typically, for prototyping, I design the PCBs, order them from OSHpark, and assemble them myself. It's fine for my designs and the current quantity, though it is time consuming. However, I'm soon reaching a point where it will take too long for a very large quantity of boards. So, I wanted to ask: how would you go about contracting out PCB design and/or assembly? Depending on the vendor, can you separate the two actions, or do you typically get one company to build and assemble your PCBs? I guess in general, what should I look for, and what mistakes should I avoid?

[Etesla]

So two things.

#1, my preferred method these days, is to use JLCPCB's SMT assembly service. The big downside there is they only do single sided assembly and you have to choose components from their predefined (but fairly vast) component library. They'll make your boards using the standard drop a .zip of your gerbers into their website type process, then you just check the box for enabling SMT assembly. From there you include 2 additional files. One is a pick and place data file, the other is a BOM. The formats for both of these files, as well as instructions for exporting specifically the pick and place files from various PCB design softwares are provided on their website. There are also a ton of youtube videos on it. If you mess it up they'll email you and tell you how to fix it. I usually only have a couple components to hand solder that they don't have in their library, but almost all jellybean stuff is there. For reference I just got 5 four layer boards completely assembled and shipped with like a 1.5 week lead time for 37 bucks. Those boards have like 11 IC's and about 90 components total for scale. You really can't beat that. They can do higher layer boards as well, you just pay more for it.

#2, have you experimented with ordering a stencil along with you PCB, placing the components by hand, and reflowing the board in your toaster oven? That was my old favorite way to do things. Probably cuts assembly time down by 4 or 5x VS hand soldering. You can do 2 sided boards this way too if you're careful about things.

At work we have boards assembled by a variety of different board houses, but the prices there come out at like 100-500 dollars a board with like a week lead time of course depending on a lot of factors, so if you got that kind of dough there are plenty of stateside options, but I don't see the point in that for personal projects...

[rpiloverbd]

In Bangladesh (where I live), there are not so many PCB printers/manufacturers. Technologies like electroplated  vias are only available to a very few high-tech industries. There are some manufacturers who print PCB in both low and bulk quantities. Such as Taru projuktee, Techshopbd etc. Most of the time, hobbyists in my country print and assemble PCB by themselves. They just buy bare CCB, ferric chloride etc and print the traces with clothes iron. This manual method saves a lot of money.

[Psi]

I've only ever used PCBway for assembly. So I cant really say if they are good or bad vs the norm.
But they seem to work ok.

If you use any china assembly service make sure you specify on the BOM if any parts are critical and give then a list of authorized sources like digikey/mouser etc.. (you can ask for their receipts copies if you are paranoid).
Otherwise they will try to source parts from companies somewhere in-between official and gray market, and you may have issues with parts that don't perform to spec.

I've not had any problems since I started giving a list of authorized sources. But sometimes you see some silkscreen on a part that is a little misaligned and you do start to wonder.

[LoveLaika]

So two things.

#1, my preferred method these days, is to use JLCPCB's SMT assembly service. The big downside there is they only do single sided assembly and you have to choose components from their predefined (but fairly vast) component library. They'll make your boards using the standard drop a .zip of your gerbers into their website type process, then you just check the box for enabling SMT assembly. From there you include 2 additional files. One is a pick and place data file, the other is a BOM. The formats for both of these files, as well as instructions for exporting specifically the pick and place files from various PCB design softwares are provided on their website. There are also a ton of youtube videos on it. If you mess it up they'll email you and tell you how to fix it. I usually only have a couple components to hand solder that they don't have in their library, but almost all jellybean stuff is there. For reference I just got 5 four layer boards completely assembled and shipped with like a 1.5 week lead time for 37 bucks. Those boards have like 11 IC's and about 90 components total for scale. You really can't beat that. They can do higher layer boards as well, you just pay more for it.

#2, have you experimented with ordering a stencil along with you PCB, placing the components by hand, and reflowing the board in your toaster oven? That was my old favorite way to do things. Probably cuts assembly time down by 4 or 5x VS hand soldering. You can do 2 sided boards this way too if you're careful about things.

At work we have boards assembled by a variety of different board houses, but the prices there come out at like 100-500 dollars a board with like a week lead time of course depending on a lot of factors, so if you got that kind of dough there are plenty of stateside options, but I don't see the point in that for personal projects...

Thanks for the reply. Sorry for not reaching back sooner. .....my hypothetical board is double-sided, but I can always make most of it single-sided, so that shouldn't be an issue other than rerouting some things. Is that typical, only having single-sided assembly? I suppose that dual-sided assembly would be harder. I never used JLCPCB as they are Chinese in origin, and we prefer US manufacturers, but I might go for it if the quality is good and the price is reasonable. Compared to something like Advanced Circuits, they certainly seem cheaper (given the price of the boards I had done by them in the past). For their component library, do they pick the parts from specific retailers like Digikey and Mouser?

2. For complex boards, I did order a stencil to use with my PCB oven, but at times, it's difficult. It's mainly for one-side for BGA components, and even then, there's still some issues. I think mainly it's my technique and solder being used. Nevertheless, the stencils were for small board batches, like less than 10, and I only used it for one side. I never used my oven for both sides of a board. I was concerned that my sensitive BGA components wouldn't handle the oven a second time around, and I was concerned about them falling off during the process. Once I had one side done, I just a used a pre-heater and a hot-air gun to finish up the rest.

[Siwastaja]

If you have no strong reason for 2-sided load, just do 1-sided assembly.

Of course with high density integration or large application processors, SoCs or FPGAs in BGA packages, you pretty much need MLCCs on the bottom side. For a QFP / QFN design, put everything on top unless very space constrained.

Note there's a difference, if you just place small 0402 bypass caps on bottom side, they don't need the glue step, they just run the board through P&P and reflow twice and the surface tension of the melting solder keeps the bottom side parts in place while they reflow the top side. Large parts on the bottom need to be glued down. All this affects the cost.

I have decent experience with PCBWay's assembly service and will be using them in future as well. I have also sourced parts myself and sent them to China. Shipping is of course quite expensive.

[T_guttata]

I'm also interested in that topic. I started doing electronics only some months ago for a specific project. I have ordered some PCBs from JLCPCB and I can't complain. I needed several iterations to get the circuit to work and I will probably need some more, so I'm glad it's cheap.
I usually ordered a PCB and a stencil as well. The stencil is actually more expensive than the PCB itself.

Now, I would also like to order some fully assembled PCBs in the future, but honestly I don't know yet how to do that. I will have some parts, which probably have to be sourced from digikey. But I don't know yet how to use components , if  they are not in the database of JLCPCB. I made some custom components, but how will JLCPCB actually do the identification of the part?

Further: how can the price be estimated? What's the minimum PCB quantity to get reasonable prices?